Abstract: A method for determining a next purchase interval of a customer is disclosed. A plurality of customer purchase records with customer identities, purchase dates, purchase intervals and purchase locations are collected. The plurality of customer purchase records are classified into individual and group purchase behaviors based on each of the purchase locations. An individual weight for the individual purchase behavior and a group weight for the group purchase behavior are calculated by Bayesian modeling. An individual purchase behavior variable based on the individual purchase behavior is generated. A group purchase behavior variable based on the group purchase behavior is generated. A next purchase interval for the customer at each of the purchase locations is determined by close form calculation using the individual weight, the individual purchase behavior variable, the group weight, and the group purchase behavior variable as inputs.